topic Re: VG in shared mode. ?? in Operating System - HP-UX

VG in shared mode. ??

rveri — Thu, 29 Jun 2006 01:42:32 GMT

All,

How to know if a volume group is activated in shared mode. Any command anything is there,

VG Name /dev/vg14
VG Write Access read/write
VG Status available, exclusive
...
--------------------------------------

Thanks,

Re: VG in shared mode. ??

Steven E. Protter — Thu, 29 Jun 2006 02:13:42 GMT

Shalom,

I believe the VG status will be different in shared mode.

Based on this, I do not believe your volume group is activated in shared mode.

There is nothing stopping you from activating a volume group in shared mode to see what it looks like. Just don't do it on a production system.

mylab1:/# vgdisplay /dev/vgemmg
--- Volume groups ---
VG Name /dev/vgemmg
VG Write Access read/write
VG Status available, exclusive
Max LV 255
Cur LV 1
Open LV 1
Max PV 16
Cur PV 1
Act PV 1
Max PE per PV 8683
VGDA 2
PE Size (Mbytes) 4
Total PE 8681
Alloc PE 8681
Free PE 0
Total PVG 0
Total Spare PVs 0
Total Spare PVs in use 0

SEP

Re: VG in shared mode. ??

Victor Fridyev — Thu, 29 Jun 2006 02:31:39 GMT

Hi,

It's not so clear what "shared mode" means.
In any case, in order to see vg status, run:

#>vgdisplay vgname |grep Status

Status "exclusive" means the vg may be used in SG cluster as a shared vg, but can not be used simultaneously by more than one computer. (vgchange -c y vgname).

Status available means that the vg may be shared and used by more than one machine, as for ORACLE RAC.

HTH

Re: VG in shared mode. ??

Mridul Shrivastava — Thu, 29 Jun 2006 02:57:17 GMT

If status is exclusive it can't be used on other node as this vg is exclusively for this node.

I am not sure but it should show shared if it is being activated in shared mode, you van try deactivating it and then activate it in shared mode using -a s option.

e Activate each specified volume
group and all associated physical
and logical volumes for exclusive
read-write access. The volume
group must be marked as part of a
high availability cluster, and the
availability software must be
running on the system; otherwise,
the volume group is not activated.

s Activate each specified volume
group and all associated physical
and logical volume for shared
read-write access. The volume
group must be marked as part of a
high availability cluster and
marked sharable; otherwise, the
volume group is not activated.

If any of the logical volumes in
the volume group are mirrored, and
if there are more than two systems
in the high availability cluster,
this volume group will not be
activated because HP MirrorDisk/UX
software is only supported in a
clustered environment with a
maximum of two nodes configured.

Re: VG in shared mode. ??

rveri — Thu, 29 Jun 2006 03:06:08 GMT

Hi,

I just wanted to reduce size of one LV and create another LV ,on that vg with the free PE/size.

While going through the man page of lvreduce found this :

# man lvreduce

...
"lvreduce cannot be performed if the volume group is activated in shared mode. "

Hence my question raised for shared mode option. Any more idea!

Thanks,

Re: VG in shared mode. ??

Chauhan Amit — Thu, 29 Jun 2006 03:36:46 GMT

Hello,

Reply is inline:

I just wanted to reduce size of one LV and create another LV ,on that vg with the free PE/size. While going through the man page of lvreduce found this :
# man lvreduce ..
"lvreduce cannot be performed if the volume group is activated in shared mode. "
Hence my question raised for shared mode option. Any more idea!

A) Looking at the above output I believe the vg14 is part of High Availability Cluster, that means a shared VG.

For a Normal VG , the output looks like
VG Status available

In your case it is showing VG Status available, exclusive

My Suggestion would be :
a)Take a downtime if it is a production system.
b) Take Backup of the LV which you want to change
c) Stop Application
c) Deactivate the Volume group from the Cluster Nodes:
#vgchange -a n /dev/vg14
d)Remove volume group from membership in the high availability cluster.
#vgchange -c n /dev/vg14
e)On this node give following command to activate VG
#vgchange -a y /dev/vg14
f)Change the LV Size
g)Deactivate VG
#vgchange -a n /dev/vg14
h)Mark volume group to be a member in the high availability cluster.
#vgchange -c y /dev/vg14

No additional Serviceguard specific steps are needed. The change is only done in the
LVM structures contained on the shared disks. Other nodes see the change
automatically, when they activate the VG.

Hope this helps.

-Amit

Re: VG in shared mode. ??

Matthew Ghofrani — Fri, 30 Jun 2006 07:29:41 GMT

I know for certain that you can increase the LV size dynamicaly even in a ServiceGuard mode on the fly (because I have done so) but you can't do lvreduce.

Please correct me if I am wrong.

Matthew from Boston

Re: VG in shared mode. ??

Roland van Lochem — Fri, 30 Jun 2006 08:17:31 GMT

# vgdisplay -v vgora
--- Volume groups ---
VG Name /dev/vgora
VG Write Access read/write
VG Status available, shared, client

Re: VG in shared mode. ??

John Hall — Wed, 05 Jul 2006 15:36:08 GMT

If a Volume Group (VG) is in shared mode a vgdisplay will look something like (notice the word "shared" on the VG Status line):

# vgdisplay vg05
--- Volume groups ---
VG Name /dev/vg05
VG Write Access read/write
VG Status available, shared, server
Max LV 255
Cur LV 212
...

When the "RAC extension" to MC/Serviceguard is installed the "-a s" option becomes available to activate the VG is shared mode:

vgchange -a s vg05

Re: VG in shared mode. ??

jhingoor — Mon, 10 Jul 2006 04:43:11 GMT

Hi guys,

do you mean if there are 2 nodes in a cluster then both their volume groups i.e. vg00 should be shared right ? i.e. the status should be shared.....

Re: VG in shared mode. ??

Steven E. Protter — Mon, 10 Jul 2006 05:15:01 GMT

Shalom,

Not really.

To be a shared volume group you need to activate it in shared mode.

vg00 is not typically activated in shared mode because its a system boot vg, though it can include other logical volumes. I believe that trying to activate vg00 in shared mode would fail or lead to catastrophic results.

If you created a volume group called vgshare or vg02 on shared storage and two cluster nodes can activate it and activate it in shared mode (-s) then your statement would be true and the posts above should help you detect it.

SEP